CN116685426A

CN116685426A - Additive manufacturing systems utilizing risley prism beam steering and related methods

Info

Publication number: CN116685426A
Application number: CN202280009225.6A
Authority: CN
Inventors: 马丁·C·费尔德曼
Original assignee: Vulcanforms Inc
Current assignee: Vulcanforms Inc
Priority date: 2021-01-08
Filing date: 2022-01-07
Publication date: 2023-09-01
Also published as: US20220219260A1; JP2024502314A; WO2022150564A1; EP4274697A1; KR20230130046A; AU2022205358A1

Abstract

Additive manufacturing systems and related methods are disclosed. In some embodiments, an additive manufacturing system includes: constructing a surface; one or more laser energy sources configured to emit laser energy; an optical phased array operatively coupled to one or more laser energy sources; and a risley prism assembly including a plurality of wedge prisms. The optical phased array includes one or more phase shifters operatively coupled to the one or more laser energy sources and configured to control a phase of the laser energy. The optical phased array is configured to direct laser energy toward the risley prism assembly, and the risley prism assembly is configured to direct laser energy toward the build surface.

Description

Additive manufacturing systems utilizing risley prism beam steering and related methods

RELATED APPLICATIONS

The present application claims the benefit of priority from U.S. c. ≡119 (e) claiming U.S. provisional application serial No. 63/135,272 filed on 1-month 8 of 2021, the disclosure of which is incorporated herein by reference in its entirety.

Technical Field

The disclosed embodiments relate to additive manufacturing systems and related methods utilizing Risley (Risley) prism beam steering.

Background

A powder bed fusion process is an example of an additive manufacturing process in which a three-dimensional shape is formed by selectively joining materials in a layer-by-layer process. During the metal powder bed melting process, one or more laser beams are scanned over the thin layer of metal powder. One or more melt pools may be established on the build surface if various laser parameters, such as laser power, laser spot size, and/or laser scan speed, are in a state where the energy delivered is sufficient to melt the metal powder particles. The laser beam is scanned along a predefined trajectory such that the solidified puddle trajectory produces a shape corresponding to a two-dimensional slice of the three-dimensional printed part. After one layer is completed, the powder surface is elevated a defined distance, the next layer of powder is spread over the build surface, and the laser scanning process is repeated. In many applications, the layer thickness and laser power density may be set to provide partial remelting of the underlying layer as well as melting of the continuous layer. The layer elevation and scanning are repeated a number of times until the desired three-dimensional shape is produced.

Disclosure of Invention

In some embodiments, an additive manufacturing system includes: constructing a surface; one or more laser energy sources configured to emit laser energy; an optical phased array operatively coupled to one or more laser energy sources; and a risley prism assembly including a plurality of wedge prisms. The optical phased array includes one or more phase shifters operatively coupled to the one or more laser energy sources and configured to control a phase of the laser energy. The optical phased array is configured to direct laser energy toward the risley prism assembly, and the risley prism assembly is configured to direct laser energy toward the build surface.

In some embodiments, a method for additive manufacturing includes: emitting laser energy from a plurality of laser energy sources; controlling a phase of laser energy emitted by each of the plurality of laser energy sources to control a shape of at least one laser beam directed onto the build surface; and adjusting the position of the at least one laser beam on the build surface using one or more wedge prisms.

In some embodiments, an additive manufacturing system includes: constructing a surface; one or more laser energy sources configured to emit laser energy; an optical phased array operatively coupled to one or more laser energy sources; and a risley prism assembly configured to control a position of the at least one laser beam on the build surface. The optical phased array is configured to control a shape of at least one laser beam directed onto the build surface.

It should be appreciated that the foregoing concepts and additional concepts discussed below may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the drawings.

Drawings

The figures are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

FIG. 1 is a schematic representation of one embodiment of an additive manufacturing system including an optical phased array assembly;

FIG. 2 depicts one embodiment of an optical phased array assembly for use in an additive manufacturing system;

FIG. 3 depicts another embodiment of an optical phased array assembly for use in an additive manufacturing system;

FIG. 4 depicts yet another embodiment of an optical phased array assembly for use in an additive manufacturing system;

FIG. 5 depicts a further embodiment of an optical phased array assembly for use in an additive manufacturing system;

FIG. 6A depicts one embodiment of a Lissley prism assembly for use in an additive manufacturing system with an optical phased array;

FIG. 6B depicts a bottom view of the optical phased array of FIG. 6A; and

FIG. 7 depicts one embodiment of a path of a pixel on a build surface.

Detailed Description

The inventors have recognized and appreciated a number of benefits associated with additive manufacturing systems that utilize one or more optical phased arrays configured to perform one or more aspects of beam manipulation during an additive manufacturing process. As used herein, an Optical Phased Array (OPA) refers to an array of light emitters (e.g., laser emitters) arranged in a one-dimensional array or a two-dimensional array, each emitting light having the same frequency. A phase shifter is associated with each transmitter, and each phase shifter is configured to control the phase of light emitted by its associated transmitter. By controlling the phase of the light emitted from each emitter, the beam formed by the superposition of light from the emitter array can be manipulated and/or shaped as desired on a build surface (e.g., a powder bed). As described in more detail below, such control of the phase shifter may be performed at a high frequency, and thus, the OPA may allow for high accuracy and high speed scanning of one or more laser beams without any physical movement of the emitter.

According to some aspects, the beam steering speed achievable with OPA may be several orders of magnitude faster than is possible using conventional methods, which may enable additive manufacturing processes that are typically higher throughput, and may also enable scanning strategies that are not possible using existing methods (e.g., galvanometer or gantry based methods). For example, in some embodiments, the laser beam may be steered by OPA on a time scale much faster than that associated with the dynamics of melting and heat transfer in the powder bed, and in this way the laser beam may be steered fast enough to effectively project an image of the laser energy onto the build surface. Furthermore, the laser beam may be shaped or otherwise dynamically controlled during the additive manufacturing process such that the beam shape may be continuously modified while scanning. This ability to control the beam shape to shapes other than gaussian during the scanning operation may be beneficial for different weld formation modes. Furthermore, the OPA-based beam manipulation system may implement the following additive manufacturing process: in this additive manufacturing process, a large number of discrete melt pools can be formed simultaneously on the build surface without sacrificing feature resolution. Furthermore, the high scan speeds achievable using OPA-based beam manipulation systems may allow laser power to be distributed over the build surface as needed, which may allow for more uniform heating of the part being formed. For example, the beam may be scanned such that no single spot is exposed to excessive laser power (which may result in undesirable defects such as keyhole porosity or other effects).

While an OPA-based beam steering system may enable beam shaping and fast and accurate scanning, the area scanned by an OPA-based system may be limited by the relatively small steering angle of the OPA. For some applications, the relatively small scan area of an OPA-based system may be limited. However, the inventors have recognized and appreciated the benefits associated with using OPA in conjunction with other types of scanning arrangements. For example, in some embodiments, a risley prism-based system may be used to perform an overall scan over a large area, while OPA may be used for finer scale scanning of the beam, as will be described in more detail below. In one such embodiment, a plurality of laser sources may be coupled with one or more optical phased arrays, and one or more risley prism assemblies may be used to perform a large scale scan of the resulting pattern on the build surface at a dimension scale that is larger than the dimension scale of the scan range of the associated OPA.

The inventors have recognized and appreciated certain additional benefits of using a risley prism-based system to perform an overall scan. The use of a risley based system may be advantageous in its ability to transmit high power laser energy. The wedge of the risley prism includes a transmissive element, such as glass, sapphire, and/or any other suitable transparent base material, which may optionally be combined with one or more high power coatings. The transmissive element may be configured to allow higher laser power than the reflective optical element (e.g., a mirror of the galvanometer assembly). That is, while mirror-based systems may be more limited in their maximum achievable laser power, risley prism-based systems may not be so limited. However, it should be understood that the systems described herein are also contemplated for use in connection with galvanometer assemblies, gantry assemblies, and other beam manipulation systems, and the present disclosure is not limited in this respect. Furthermore, the use of a risley prism based system may be advantageous in its ability to transmit laser energy with greater accuracy and fidelity. For example, the wedge of a risley prism may be a planar element. In this way, the wedge may direct the individual wavefronts emitted by the optical phased array in the same direction. In contrast, conventional beam forming optics (e.g., a telescope assembly) can direct individual wavefronts into different directions based on the position of each wavefront contact lens.

In some embodiments, the OPA may be arranged in series with the risley prism assembly such that the laser beam output from the OPA is directed toward the risley prism assembly. The small scale adjustment by OPA may cooperate with the large scale adjustment by risley prism assembly to achieve highly accurate, high speed scanning and/or beam shaping of one or more laser beams over a large area of the build surface of the additive manufacturing system.

The risley prism assembly may include one or more wedge prisms configured to adjust the angle of the beam relative to the build surface. The wedge prism may include an input surface and an output surface opposite the input surface and oriented at an angle relative to the input surface. Without wishing to be bound by theory, light passing through the wedge prism may be refracted due to the angular difference between the input surface and the output surface. Furthermore, in some embodiments, the input and output surfaces of the wedge prism may be planar.

Each wedge prism in the risley prism assembly may be coupled to an actuator such that actuating the actuator may rotate the wedge prism. Suitable actuators include, but are not limited to: brushless DC motor, brush DC motor, stepper motor and servo motor. In various embodiments disclosed herein, the wedge prism may be configured to rotate about: an axis perpendicular to its input surface; an axis perpendicular to its output surface; an axis perpendicular to the build surface; an axis perpendicular to the output surface of the OPA assembly; combinations of the foregoing and/or any other suitable axes of rotation, the present disclosure is not limited in this respect.

As the wedge prism rotates, the direction of light exiting the wedge prism may also rotate. By adjusting the angle at which the light leaves the wedge prism, the location at which the light impinges on the surface downstream of the wedge prism can be controlled. Without wishing to be bound by theory, if the position at which light strikes the input surface of the wedge prism remains constant, rotating the wedge prism may cause light to pass through the wedge prism and exit the output surface of the wedge prism to trace a circle on the surface downstream of the wedge prism.

By combining two or more wedge prisms in series, the risley prism assembly may be configured to create a complex light path. For example, laser energy output from the OPA may be passed through a first wedge prism of the risley prism assembly, thereby refracting the laser energy. After passing through the first wedge prism, the laser energy may contact the input surface of the second wedge prism. The location at which the laser energy contacts the input surface of the second wedge prism may be based at least in part on: the angular position of the first wedge prism (as determined by how much the actuator rotates the first wedge prism), the angle of refraction of the laser energy as it passes through the first wedge prism (as determined by the relative angles of the input and output surfaces of the first wedge prism), and the distance between the first wedge prism and the second wedge prism. The laser energy may then be passed through a second wedge prism to again refract the laser energy. In this way, the laser energy may be continuously refracted by each wedge prism in the risley prism assembly until the laser energy reaches the build surface. By actuating actuators associated with one or more wedge prisms in the risley prism assembly, the wedge prisms may be rotated and laser energy may be directed onto the build surface.

In general, the term "risley prism assembly" is not limited to any particular number or arrangement of wedge prisms, and it should be understood that the risley prism assembly may include any suitable number of wedge prisms or other optical elements. As used herein, the term "risley pair" refers to a pair of wedge prisms. That is, "risley prism pair" refers to a risley prism assembly having two wedge prisms. As used herein, the term "dual risley pair" refers to two risley pairs, which thus include four wedge prisms.

It should be appreciated that the wedge prisms of the risley prism assembly may be rotated in any suitable direction and at any suitable speed, as the present disclosure is not limited in this respect. For example, if the risley prism assembly includes two wedge prisms, the two wedge prisms may rotate in the same direction and/or in opposite directions about a common axis of rotation. Furthermore, each of the two wedge prisms may be rotated at any suitable speed, regardless of the speed at which the other of the two wedge prisms is rotated.

As described above, the wedge prism of the risley prism assembly may be a transmissive element comprising glass and/or a high power coating. Without wishing to be bound by theory, the material of the wedge prism may be selected based at least in part on the transmissive properties of the material. For example, it may be desirable for the wedge prism to transmit and/or refract laser energy without absorbing undesirable energy levels that would heat the wedge prism. In some embodiments, the wedge prism may be made of glass. In some embodiments, the wedge prism may be made of fused silica material. Non-limiting examples of suitable materials include Corning (Corning) 7980, corning 7979, materials from He Lishi (Heraeus) infrared silicon (infra) and/or materials from transparent quartz (super sil). In some embodiments, the wedge prism may be made of sapphire. In some embodiments, the base material of the wedge prism may be coated. The coating may be applied using sputtering, ion beam magnetron sputtering, evaporation, and/or any other suitable method to apply the coating to the transparent base material. Of course, it should be understood that the wedge prisms of the risley prism assembly may be made of other suitable materials and that the present disclosure is not limited in this respect.

In some embodiments, the additive manufacturing system can include one or more laser energy sources coupled to the OPA. The OPA may be positioned above a build surface (e.g., a powder bed comprising metal or other suitable material) of the additive manufacturing system, and the OPA may be configured to direct laser energy from one or more laser energy sources toward the build surface and scan the laser energy along the build surface in a desired shape and/or pattern to selectively melt and fuse material on the build surface. In some implementations, a risley prism assembly may be positioned after or downstream of the OPA and configured to further adjust the position of the laser energy output from the OPA on the build surface.

In some embodiments, the OPA may be formed from an array of optical fibers having an emitting surface directed toward the powder bed. For example, the fiber array may have ends secured in fiber holders constructed and arranged to hold the fibers in a desired one-dimensional or two-dimensional pattern. However, it should be appreciated that the fiber array may have an emission surface that is directed in a direction other than toward the powder bed, as the direction of light emitted by the fibers may be redirected using one or more mirrors, prisms, lenses, or other suitable light directing components, as the disclosure is not limited in this respect. In some cases, each optical fiber may be coupled to an associated laser energy source. Alternatively, one or more laser energy sources may be coupled to the dividing structure to couple laser energy from the laser energy sources to the fiber array. Each fiber in the fiber array may be coupled to an associated phase shifter, but embodiments in which the laser energy emitted by the fiber array is optically coupled to an associated phase shifter may also include free space optical connections, as the disclosure is not limited to how the laser energy source is coupled to the phase shifter. In some embodiments, the phase shifter may be a piezoelectric phase shifter constructed and arranged to stretch a portion of an associated optical fiber in response to an electrical signal to change the phase of laser energy emitted from the optical fiber. As described below, in some embodiments, the system may further include one or more sensors configured to detect the phase of the laser energy emitted from each fiber in the array, which may be used in a feedback control system for controlling one or more beams formed and scanned by the OPA.

In some embodiments, the OPA may be formed using a free space phase shifter. For example, an array of laser energy pixels may be projected from an array of optical fibers. One or more mirrors, lenses, prisms, or other optical elements may be used to direct, shape, and/or focus the laser energy array toward the free space optical shifter array, and the phase of each laser energy pixel may be controlled as it passes through the free space phase shifter such that the superposition of phase shifted laser energy pixels exiting the phase shifter forms one or more laser energy beams that are manipulated, shaped, and/or controlled as desired.

In some embodiments, one or more OPAs may be formed on a semiconductor substrate. For example, a semiconductor substrate (e.g., a silicon wafer) may have a plurality of waveguides formed thereon, and each waveguide may terminate in an emitter constructed and arranged to emit light (e.g., laser energy) from the semiconductor substrate. According to a particular embodiment, the emitter may be formed as a so-called vertical emitter, such as a grating emitter that emits light substantially perpendicular to the semiconductor substrate, or an edge emitter that is configured to emit light from an edge of the semiconductor substrate. In the case of an edge emitter, in some embodiments, multiple edge emitting structures may be stacked to form a two-dimensional array. Furthermore, each emitter may have an associated phase modulation structure formed on the semiconductor substrate, and the phase modulation structure may be controlled to control the phase of the light emitted by each emitter, allowing control of the resulting beam emitted by the OPA. The waveguide formed on the semiconductor substrate may be optically coupled to one or more light sources, such as one or more high power laser energy sources, and the waveguide may transmit light through the semiconductor substrate to the emitter. In some cases, one or more dividing structures may be formed on the semiconductor substrate to divide light coupled to the semiconductor substrate between the plurality of emitters. It will be appreciated that the semiconductor structures described above may be fabricated and arranged in any suitable manner. For example, photolithographic processes known in the art may be used, but any suitable method of fabricating the described structures may be used as the present disclosure is not limited thereto.

In some cases, OPAs formed on a semiconductor substrate may undesirably absorb heat (e.g., due to transmission loss and/or emission of light toward the substrate) while laser energy is being transmitted through the waveguide and/or while laser light is being emitted from the emitter. Such heat may cause damage to the semiconductor structure, especially at laser power levels suitable for additive manufacturing processes. Thus, in some embodiments, a semiconductor substrate having an OPA structure formed thereon may be coupled to a cooling structure (e.g., a heat sink or cooling plate) that may be configured to actively cool the semiconductor substrate and the OPA structure. For example, an OPA assembly or a substrate (e.g., a semiconductor substrate) including a portion of the OPA assembly may be mounted on the cooling structure.

According to some aspects, the inventors have appreciated that it may be desirable to control the spacing of emitters in an OPA. For example, and without wishing to be bound by any particular theory, it may be desirable to maintain the spacing between adjacent emitters at about half the wavelength of the light emitted from the OPA to reduce unwanted side lobes or grating lobes that may form when the emitters of the phased array are separated by a large distance. Thus, in some embodiments, OPAs according to the present disclosure may have emitter spacing selected based on the wavelength of laser energy used in the additive manufacturing process. For example, in some cases, the laser energy may have a wavelength of about one micron, and thus the OPA may be configured with emitters spaced about 0.5 microns apart from each other.

Depending on the particular implementation, the phase shifter of the OPA may be operatively coupled to a controller configured to control the phase of the light emitted by each emitter of the OPA. In some cases, each phase shifter may be capable of operating at very high frequencies (e.g., frequencies of hundreds of MHz to several GHz). Thus, the controller may be configured to send a high frequency control signal to operate the phase shifter and to steer and/or shape one or more beams emitted by the OPA. For example, in some embodiments, the controller may include one or more Field Programmable Gate Array (FPGA) structures operatively coupled to the phase shifter. In one exemplary embodiment, an OPA formed on a semiconductor substrate may include one or more FPGA structures formed on the same semiconductor substrate and coupled to a phase shifter of the OPA via interconnects formed on the substrate. In this way, the OPA and controller can be formed as a single integrated device on a semiconductor substrate. In some embodiments, one or more actuators of the risley prism assembly may be operatively coupled to the controller. In some implementations, a single controller may be configured to control both the OPA and the risley prism assembly to coordinate beam adjustment associated with the OPA and beam adjustment associated with the risley prism assembly. However, it is also contemplated that separate controllers may be used for the various components described herein.

As used herein, a controller may refer to one or more processors operatively coupled to a non-transitory processor-readable memory that includes processor-executable instructions that, when executed, cause various systems and components to perform any of the methods and processes described herein. It should be appreciated that any number of processors may be used such that a process may be performed on a single processor or multiple distributed processors that are located at any suitable location, including within and/or remote from the additive manufacturing system, as the present disclosure is not limited in this manner.

In some embodiments, the scanning speed of an additive manufacturing system comprising an OPA assembly and a risley assembly may depend at least in part on the individual scanning speeds of the OPA assembly and the risley assembly. As described above, the phase shifter of the OPA assembly may be capable of operating at very high frequencies, for example, at maximum operating frequencies between 1MHz and 100GHz or equal to 1MHz and 100 GHz. For a desired application, the risley prism assembly may be scanned at any suitable speed, where the speed may depend at least in part on motor specifications, wedge weight, wedge inertia, and/or beam position. While the risley prism assembly itself may be capable of scanning at high speeds, the inventors have recognized that in the absence of an OPA assembly, the individual risley prism assemblies may be limited. To achieve a complex beam path using a separate risley prism assembly (i.e., not in combination with the OPA assembly), it may be necessary to turn the laser energy on and off at very high frequencies. Coordinating the timing between modulating the laser energy and adjusting the risley prism may present certain challenges. Furthermore, switching the laser energy on and off at high frequencies may be associated with power distribution and pulse energy that may be undesirable. However, the inventors have realized that the use of an OPA assembly in combination with a risley prism assembly can achieve beam shaping with extremely high speeds and advantageous power distribution.

Turning to the various figures, specific non-limiting embodiments are described in further detail. It should be understood that the various systems, components, features, and methods described with respect to these embodiments may be used alone and/or in any desired combination, as the present disclosure is not limited to the specific embodiments described herein.

Fig. 1 is a schematic representation of one embodiment of an additive manufacturing system 1, the system comprising an OPA assembly 10, the OPA assembly 10 being constructed and arranged to manipulate a laser energy beam 2 along a build surface 4. As shown, the OPA may be arranged to direct the beam within an angular scanning range 6, which angular scanning range 6 may be up to 40 degrees, up to 60 degrees, up to 90 degrees, up to 120 degrees, up to 150 degrees or more. As mentioned above, the OPA can steer the beam via controlling the high frequency phase shifter in the OPA, and thus the effective scanning speed of the beam over the build surface 4 can be more than 10m/s, more than 50m/s, more than 100m/s, more than 1000m/s or more. In some embodiments, the effective scanning speed of the beam on the build surface 4 may be below 10000m/s, below 1000m/s, below 100m/s or below 50m/s. Thus, OPA may enable scanning of the beam such that its defined image or pattern is virtually static on a time scale associated with a powder melting process (e.g., melting and solidification of metal powder).

Given the relatively high speed at which the laser beam can scan across the surface of the powder bed, the formation process may function somewhat like an electron beam-based powder bed-based machine. In particular, one or more laser beams may be scanned across the powder bed in a pattern and at a speed such that one or more corresponding melt fronts do not advance along the primary direction of motion of the one or more laser beams. Instead, the melt front may travel in a secondary direction of motion, i.e., in the direction of motion of an image produced by one or more beams scanning across the powder bed. This may be beneficial compared to typical laser-based systems, as it may be possible to expose a relatively large area, bring more power than with a single spot, and provide more uniform thermal heating of the part being formed. However, while specific scan speeds of the laser across the powder bed surface are mentioned above, scan speeds greater than and less than the above scan speeds are contemplated as the present disclosure is not limited in this manner.

As shown, the OPA assembly 10 may be optically coupled to one or more laser energy sources 12 (e.g., via one or more fiber optic cables) and operatively coupled to a controller 14, the controller 14 configured to control the phase shifters of the OPA to steer and/or shape the beam 2. As described above, in some cases, the controller may include a high-speed FPGA coupled to the phase shifter to enable high-frequency operation and control of the OPA. Further, a controller as described herein may include one or more processors and associated non-transitory processor-readable memory or other medium storing instructions that, when executed by the one or more processors, may control the systems and components described herein to perform the disclosed methods and operations.

Fig. 2 depicts one embodiment of an OPA assembly 100 that may be used to direct laser energy onto a build surface of an additive manufacturing system. The system includes a laser energy source 102, which may be referred to as a seed laser. Laser energy is transmitted from the source 102 to the coupler 104, which coupler 104 splits the laser energy into a plurality of optical fibers that transmit the laser energy to a plurality of optical fiber phase shifters 106, such as piezoelectric fiber phase modulator tensioners arranged to tension the optical fibers to modulate the phase of the laser energy passing through the optical fibers. The laser energy in each fiber or transmitted along different optical paths may be substantially in phase with each other and may have the same wavelength or wavelength range prior to entering the phase shifter. Once the laser energy passes through the phase shifter, the modulated (i.e., phase shifted) laser energy is then transmitted through a plurality of amplifiers 108, the plurality of amplifiers 108 being configured to amplify the power of the laser energy to a desired power level (e.g., a power level suitable for a powder melting process). The ends of the optical fibers exiting the amplifier 108 are housed in a fiber holder 110, which fiber holder 110 may be constructed and arranged to arrange the fiber ends to form a desired pattern of laser energy emitters, such as a one-dimensional or two-dimensional array. The fiber holders may be configured in any suitable manner to arrange the optical fibers in a desired pattern. For example, a plate or other structure may include a plurality of precision bores to which optical fibers may be individually connected to arrange the optical fibers in a desired pattern. Other configurations of fiber optic holders may be used as the present disclosure is not limited thereto. In some embodiments, the optical fiber may include multiple cores, which may further reduce emitter spacing in some applications.

In some embodiments, the OPA assembly may further include a phase detector 112 to detect the phase of laser energy emitted from the optical fiber held in the fiber holder 110, which phase detector 112 may be used in a feedback control system as described below. Depending on the implementation, feedback control may be implemented using one or more sensors located inside or outside the OPA assembly, as the present disclosure is not limited to how feedback control is implemented. Further, in some embodiments, the laser energy transmitted from the fiber holder 110 may pass through one or more optical elements 114, such as lenses, before being directed to the build surface. As shown, the controller 116 is coupled to the laser energy source 102, the phase shifter 106, and the phase detector. The controller may control the operation of each of these components to achieve a desired shape and/or pattern of laser energy emitted from the fiber holder 110 toward the build surface and through the optical element 114 (if included). In some implementations, the controller may utilize an active feedback scheme to control the phase of the laser energy passing through each phase shifter 106 based on the phase measured using detector 112.

Fig. 3 depicts another embodiment of an OPA assembly 200. Similar to the previously described embodiments, the OPA assembly 200 includes an optical fiber holder 206, the optical fiber holder 206 being constructed and arranged to hold the ends of the optical fibers in a desired pattern of laser energy emitters, such as a one-dimensional or two-dimensional array. However, in this embodiment, each emitter of the array has an associated laser energy source 202, rather than utilizing a single laser energy source that is subsequently segmented. In particular, the OPA assembly 200 includes a plurality of laser energy sources 202, the laser energy sources 202 being coupled to a phase shifter 204 and subsequently to a fiber holder 206. Similar to the embodiments described above, the phase detector 208 may detect the phase of laser energy emitted from the emitter held in the fiber holder 208 for use in a feedback control scheme, and the assembly may further include one or more optical elements 210 between the fiber holder 206 and the build surface. Further, a controller 212 is operatively coupled to the laser energy source 202, the phase shifter 204, and the phase detector 208.

Fig. 4 depicts another embodiment of an OPA assembly 300. In this embodiment, laser energy from a laser energy source 302 is split and coupled to a fiber holder 306 via a coupler 304. Similar to the embodiments described above, the fiber holder may define an array of laser energy emitters. In this embodiment, laser energy may be emitted from an emitter array and then passed through a plurality of free space phase shifters 308, the phase shifters 308 configured to modulate the phase of the laser energy and to manipulate and/or shape the resulting beam of laser energy. As shown, the phase shifter may be positioned between optical elements 310, such as lenses, and the optical elements 310 may focus and/or direct laser energy from the fiber holder 306 to the phase shifter 308. In some cases, these optical elements may be configured to shape the laser energy emitted from the fiber holder 306 to reduce the spacing between adjacent laser energy wavefronts emitted from the fiber holder prior to phase shifting via the free space phase shifter 308. In some cases, the spacing may be reduced to about half the wavelength of the laser energy, which may help reduce undesirable side lobes (as discussed above). The phase shifters 308 may be operatively coupled to a controller 312 to control the phase of the laser energy passing through each of the phase shifters to steer and/or shape the resulting laser energy beam. In some cases, one or more additional optical elements 310 may be placed after the phase shifter.

Fig. 5 depicts yet another embodiment of an OPA assembly 400 that may be used in an additive manufacturing system. In this embodiment, OPA is formed on a semiconductor substrate such as a silicon wafer. In this embodiment, laser energy from a laser energy source 402 is coupled to a semiconductor substrate 404 and the laser energy is transmitted to a plurality of emitters 406 formed on the substrate 404 via waveguides 410 formed on the substrate 404. For example, the emitter 406 may be configured as a grating emitter configured to emit laser energy in a direction substantially perpendicular to the plane and/or surface of the substrate. The laser energy may be transmitted through a plurality of phase modulators 408 formed on the semiconductor substrate before reaching the emitter, and the phase modulators may be operatively coupled to a controller 412. In some cases, the controller may also be formed on the semiconductor substrate such that the OPA assembly 400 may be formed as a single integrated component.

Fig. 6A depicts one embodiment of an additive manufacturing system 550 comprising an optical phased array and a risley prism assembly. In the depicted embodiment, the beam 504 output from the OPA assembly 502 may be directed toward the risley prism assembly 500. In the embodiment of the figures, the risley prism assembly 500 includes a first wedge prism 508a, a second wedge prism 508b, a third wedge prism 508c, and a fourth wedge prism 508d. Each wedge prism may be operatively coupled to an associated actuator. In some embodiments, the wedge prism may be coupled to the actuator by a transmission. In some embodiments, a single actuator may be coupled to multiple wedge prisms. In the embodiment of the figures, wedge prisms 508 a-508 d are coupled to actuators 509 a-509 d (respectively) by transmissions 510 a-510 d (respectively).

The first wedge prism 508a and the second wedge prism 508b form a first risley pair and the third wedge prism 508c and the fourth wedge prism 508d form a second risley pair. The first pair of risley prisms and the second pair of risley prisms form a double risley pair. In other embodiments, other numbers of wedge prisms may be included in a risley prism assembly, and the present disclosure is not limited to risley prism assemblies including four wedge prisms.

In the embodiment of the figure, the input surface 520a of the first wedge prism 508a is oriented at an angle relative to the output surface 521a of the first wedge prism. Although not labeled in fig. 6A for clarity, each wedge prism 508 a-508 d includes an input surface oriented at an angle relative to an output surface. In a risley pair (e.g., first and second wedge prisms 508a and 508b or third and fourth wedge prisms 508c and 508 d), the output surface of the first wedge prism in the risley pair may be parallel to the input surface of the second wedge prism in the risley pair, which may also be parallel to the build surface 506 in some embodiments. However, it should be understood that the particular arrangement of wedge prisms in fig. 6A and their relative orientations (as well as orientations and positions relative to a build surface) are merely examples of one possible implementation, and the present disclosure is not limited to the implementation of this figure.

In the embodiment of fig. 6A, the beam 504 output from the OPA assembly 502 is refracted as the beam 504 passes through each wedge prism 508 a-508 d of the risley prism assembly 500. Rotating the wedge prism may adjust the angle at which beam 504 exits the wedge prism. Thus, by controlling both the relative rotational position and the absolute rotational position of wedge prisms 508 a-508 d of risley prism assembly 500, the additive manufacturing system can manipulate the position of beam 504 on build surface 506 over a larger area than is possible using OPA assembly itself. Again, this may allow for fast and accurate control of both the position and shape of the laser beam directed onto the build surface.

It should be appreciated that although only a single beam 504 is depicted in the figures, any suitable number of beams arranged in any suitable arrangement may be used to provide a desired wavefront pattern or image for an additive manufacturing system having OPA and risley prism assemblies, as the disclosure is not limited in this respect. Further, while a single OPA and associated risley prism assembly are depicted, the additive manufacturing system may include any suitable number of OPAs and associated risley prism assemblies for cooperating with large-scale scanning of the pattern output by the individual OPAs over the build surface of the additive manufacturing system.

The OPA module 502 may be optically coupled to one or more laser energy sources 512 (e.g., via one or more fiber optic cables). Fig. 6B depicts a bottom view of the OPA assembly 502 of fig. 6A, showing a plurality of pixels that may correspond to respective laser beams output by the OPA assembly. The OPA module 502 may also be operatively coupled to a controller 514, the controller 514 being configured to control the phase shifters of the OPA to steer and/or shape the beam 504. The controller 514 may additionally be coupled to actuators 509 a-509 d and/or transmissions 510 a-510 d associated with the wedge prisms 508 a-508 d. As described above, in some cases, the controller may include a high-speed FPGA coupled to the phase shifter to enable high-frequency operation and control of the OPA. Further, a controller as described herein may include one or more processors and associated non-transitory processor-readable memory or other medium storing instructions that, when executed by the one or more processors, may control the systems and components described herein to perform the disclosed methods and operations.

Fig. 7 depicts one embodiment of a path 610 of pixels across build surface 606 due at least in part to operating a risley prism. Without wishing to be bound by theory, a risley prism may be used to create a regularly repeating pattern, also known as a rose curve. Lines, circles, ellipses, and other shapes may be created using risley prisms. In some embodiments, the discontinuous pattern may be created, for example, by rotating wedges of the risley prisms at a non-constant speed. By combining the risley prism assembly with the OPA assembly, virtually any pattern can be achieved without limitation.

The above-described embodiments of the technology described herein can be implemented in any of a number of ways. For example, embodiments may be implemented using hardware, software, or a combination thereof. When implemented in software, the software code can be executed on any suitable processor or collection of processors, whether disposed in a single computer or distributed among multiple computers. Such a processor may be implemented as an integrated circuit having one or more processors in an integrated circuit component, including commercially available integrated circuit components known in the art as, for example, CPU chips, FPGAs, GPU chips, microprocessors, microcontrollers, or co-processors. In the alternative, the processor may be implemented in custom circuitry, such as an ASIC, or in semi-custom circuitry resulting from the configuration of a programmable logic device. As another alternative, the processor may be part of a larger circuit or semiconductor device (whether commercially available, semi-custom or custom made). As a specific example, some commercially available microprocessors have multiple cores such that one or a subset of the cores may constitute the processor. However, the processor may be implemented using circuitry in any suitable format.

While the present teachings have been described in connection with various embodiments and examples, it is not intended to limit the present teachings to such embodiments or examples. Aspects of the present disclosure may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. The present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. Accordingly, the foregoing description and drawings are by way of example only.

Claims

1. An additive manufacturing system, comprising:

constructing a surface;

one or more laser energy sources configured to emit laser energy;

an optical phased array operatively coupled to the one or more laser energy sources, the optical phased array comprising one or more phase shifters operatively coupled to the one or more laser energy sources and configured to control a phase of the laser energy; and

A risley prism assembly comprising a plurality of wedge prisms,

wherein the optical phased array is configured to direct the laser energy toward the risley prism assembly,

wherein the risley prism assembly is configured to direct the laser energy toward the build surface.

2. The additive manufacturing system of claim 1, wherein the risley prism assembly comprises a dual risley prism pair.

3. The additive manufacturing system of claim 1, further comprising a processor operatively coupled to the optical phased array and the risley prism assembly, wherein the processor is configured to control a position of one or more laser energy beams directed toward the build surface by controlling a phase of the laser energy with the optical phased array, and wherein the processor is configured to control a position of one or more laser energy beams directed toward the build surface by controlling an angular position of the one or more wedge prisms of the risley prism assembly.

4. The additive manufacturing system of claim 3, further comprising one or more sensors configured to detect a phase of laser energy emitted from the one or more laser energy sources, and wherein the processor is configured to control the phase of laser energy emitted from the one or more laser energy sources based at least in part on the detected phase.

5. The additive manufacturing system of claim 1, wherein the optical phased array is configured to scan one or more laser energy beams along the build surface at a speed of at least 10 m/s.

6. The additive manufacturing system of claim 1, wherein the optical phased array comprises a semiconductor substrate having a plurality of waveguides, emitters, and phase shifters formed thereon.

7. The additive manufacturing system of claim 6, wherein the semiconductor substrate is mounted on a cooling structure configured to remove heat from the semiconductor substrate.

8. The additive manufacturing system of claim 6, wherein the emitters are arranged in a two-dimensional array and the emitters are configured to emit in a direction perpendicular to a surface of the substrate.

9. An additive manufacturing system according to claim 6, wherein the emitter is arranged to emit from an edge of the semiconductor substrate.

10. The additive manufacturing system of claim 6, wherein the emitter comprises a plurality of edge emitting structures stacked to form a two-dimensional array.

11. The additive manufacturing system of claim 1, wherein each of the wedge prisms of the risley prism assembly is a planar wedge prism configured to direct a wavefront of laser energy from the optical phased array in a single direction.

12. A method for additive manufacturing, the method comprising:

emitting laser energy from a plurality of laser energy sources;

controlling a phase of laser energy emitted by each of the plurality of laser energy sources to control a shape of at least one laser beam directed onto the build surface; and

the position of the at least one laser beam on the build surface is adjusted using one or more wedge prisms.

13. The method of claim 12, wherein controlling the phase of the laser energy comprises: an optical phased array is used to control the phase of the laser energy.

14. The method of claim 13, wherein controlling the phase of the laser energy with the optical phased array comprises: a plurality of phase shifters is utilized to control the phase of the laser energy.

15. The method of claim 12, further comprising: detecting a phase of laser energy emitted by each of the plurality of laser energy sources; and controlling the phase of the laser energy emitted by each of the plurality of laser energy sources based at least in part on the detected phase of the laser energy emitted by each of the plurality of laser energy sources.

16. The method of claim 12, further comprising: controlling a phase of laser energy emitted by each of the plurality of laser energy sources to scan the at least one laser beam along the build surface.

17. The method of claim 16, further comprising: the at least one laser beam is scanned along the build surface at a speed of at least 10 m/s.

18. The method of claim 12, wherein adjusting the position of the at least one laser beam on the build surface with the one or more wedge prisms comprises: at least one wedge prism of the one or more wedge prisms is rotated about an axis perpendicular to the build surface.

19. The method of claim 18, wherein rotating at least one of the one or more wedge prisms comprises: at least one wedge prism of the at least one pair of wedge prisms of the risley prism assembly is rotated.

20. The method of claim 19, wherein rotating at least one wedge prism of the at least one pair of wedge prisms of the risley prism assembly comprises: at least one wedge prism of the two pairs of wedge prisms of the pair of double risley prisms is rotated.

21. An additive manufacturing system, comprising:

constructing a surface;

one or more laser energy sources configured to emit laser energy;

an optical phased array operatively coupled to the one or more laser energy sources, the optical phased array configured to control a shape of at least one laser beam directed onto a build surface; and

a risley prism assembly configured to control a position of the at least one laser beam on the build surface.

22. The additive manufacturing system of claim 21, wherein the optical phased array is configured to direct the at least one laser beam toward the risley prism assembly, and wherein the risley prism assembly is configured to direct the at least one laser beam toward the build surface.

23. The additive manufacturing system of claim 21, wherein the risley prism assembly comprises a plurality of wedge prisms.

24. The additive manufacturing system of claim 23, wherein each wedge prism of the plurality of wedge prisms is configured to rotate about an axis perpendicular to the build surface.

25. The additive manufacturing system of claim 24, wherein the risley prism assembly is configured to control the position of the at least one laser beam on the build surface by rotating at least one wedge prism of the plurality of wedge prisms.

26. The additive manufacturing system of claim 21, wherein the optical phased array comprises one or more phase shifters configured to control a phase of the laser energy.

27. The additive manufacturing system of claim 21, further comprising a processor operatively coupled to the optical phased array and the risley prism assembly, wherein the processor is configured to control the position of the at least one laser beam on the build surface by adjusting the optical phased array and/or the risley prism assembly.